The present invention relates to a method and apparatus for reading data from a recording medium to reproduce original data from the thus-read data at high speed.
Recorded data are read from a hard disk, such as a magnetic disk, an optical disk, or a Digital Video disk (DVD) by means of a read head and are in the form of an analog read signal. The analog read signal is converted into a digital signal by an A/D converter incorporated in a read channel IC, and the digital signal is subjected to various types of digital processing. The thus-processed signal is output to a data reproduction section composed of a DSP, a microcomputer, or the like. The data reproduction section reproduces the original recorded data read from the disk. In recent years, in order to speed up the reproduction of the recorded data, attempts have been made to improve a recording density of the recording medium and a rate at which a digital signal is processed. Accordingly, in order to speed up the digital processing rate, a high-speed interface between the read channel IC and the data reproduction is required.
In the prior art, an analog signal read from a hard disk via a read head is input to a read channel IC. In the read channel IC, the input analog signal is converted into a digital signal by an A/D converter, and the digital signal is subjected to predetermined demodulation processing. The digital signal is converted from a serial signal into a parallel signal comprising a given number of bits and is output to a data reproduction section, i.e., a DSP, a microcomputer, or the like.
In order to cope with an increase in the speed of reproduction of recorded data in recent years, the manner of recording data on a hard disk has been modified such that a plurality of synch-bytes (synchronization bytes) are stored in each sector, and for each synch-byte, record data, a preamble signal, and a training signal are stored, along with an ECC (error checking and correcting) code, in each sector.
The synch-byte is provided for synchronizing an operation for reading each piece of recorded data, and the preamble signal and the training signal include signals for setting coefficients of a filter and an amplifier incorporated in the read channel IC, or a ratio of frequency division of a PLL (Phase Locked Loop) circuit.
The read channel IC subjects these signals and the recorded data, both of which are read from each sector, to predetermined processing and outputs the thus-processed signal and data to the data reproduction section. Further, the read channel IC outputs a synch-byte detection signal-which indicates whether or not each synch-byte has been correctly read-to the data reproduction section.
The data reproduction section reproduces original data from the recorded data received from the read channel IC. At this time, so long as the synch-byte detection signal indicates that at least one synch-byte in each sector has been correctly read, even if the other synch-bytes are not correctly read, original data corresponding to the other synch-bytes can be reproduced on the basis of the recorded data corresponding to the correctly-read synch-byte and the ECC code.
In the foregoing recorded data reproduction apparatus, the preamble signal and the training signal are input to the data reproduction section along with the recorded data and the synch-byte output from the read channel IC. The correctly-read recorded data are extracted from the recorded data and the signals on the basis of the synch-byte detection signal, and the original data are reproduced from the recorded data.
As described above, since the operation for extracting the recorded data on the basis of the synch-byte detection signal and the operation for reproducing the original data from the thus-detected recorded data are both executed by the data reproduction section, a data reproduction section employing a slow-speed DSP or microcomputer cannot reproduce the original data from the recorded data which are read while a recent high-recording-density hard disk is rotated at high speed. As a result, in order to increase the data reproduction rate, a high-speed DSP or microcomputer must be used as the data reproduction section, which increases the cost of the recorded data reproduction apparatus. Accordingly, it would be advantageous to provide a method and an apparatus for reproducing recorded data to enable high-speed data reproduction while preventing an increase of cost.